Method for producing bio-heavy oil from sewage sludge and bio-heavy oil produced by the method

ABSTRACT

The present disclosure relates to a method for producing a sewage sludge-derived bio-heavy oil and the bio-heavy oil produced by the method, the method including breaking organic materials included in the sewage sludge into small molecules and removing oxygen at the same time using a supercritical state alcohol as a solvent and reaction medium, thereby effectively providing a bio-heavy oil with low oxygen content and high energy content.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0128513, filed on Sep. 10, 2015, in the Korean Intellectual Property office, the entire contents of which are incorporated herein by reference in their entirety.

BACKGROUND

Field

The present disclosure relates to a method for producing bio-heavy oil from sewage sludge and the bio-heavy oil produced by the method, and more particularly, to a method for producing bio-heavy oil using sewage sludge as raw material and using alcohol at a supercritical state as solvent and reaction medium to crack organic material existing inside the sewage sludge, break the organic material into small molecules and remove oxygen at the same time, in order to produce a liquid state bio-heavy oil having a low oxygen content and an increased energy content, that can be utilized as a liquid phase fuel for use of power generation or as a liquid phase fuel for use of transportation hereafter upgrading in the future, and the bio-heavy oil produced by the method.

Description of Related Art

Recently, as the concerns over environment pollution such as depletion of petroleum resources and CO₂ emission due to overuse of fossil fuels increase, there is a surge of interest in renewable, sustainable and environmentally-friendly fuels based on non-fossil fuels. Sewage sludge is an organic byproduct that is generated inevitably in the process of treating sewage. Examples of types of sludge being generated in sewage treatment processes according to the standard activated sludge method that is one of the sewage treatment methods mostly adopted by domestic and overseas sewage treatment plants include: raw sludge, the sludge generated from initial sedimentation basins, the concentration of solid material being 4 to 10 weight %; excess sludge, the sludge collected from final sedimentation basins excluding return sludge, the concentration of solid material being 0.8 to 2.5 weight %; enriched sludge, the sludge enriched in a sludge thickener, the concentration of solid material being 2 to 8 weight %; digested sludge, the sludge processed in a digestion tank, the concentration of solid material being 2.5 to 7 weight %; and dehydrated sludge, the sludge of which moisture has been reduced by a dehydrator, the concentration of solid matter being 20 weight %, etc. Sewage sludge contains various kinds of organic materials in abundance, and thus by applying adequate technologies to such organic materials, it is possible to collect energy from them.

Meanwhile, due to the increase of population in big cities worldwide and the rapid enhancement of living standards, the amount of sewage being generated in sewage treatment plants continues to increase. For example, the amount of sewage sludge generated in South Korea increased from 7,446 tons/day in 2006 to 10,179 tons/day in 2015, showing a rapid increase rate of 40% during the past 10 years. However, sewage sludge landfill sites are limited and there are difficulties in obtaining landfill sites. Further, as the London Dumping Convention went into effect recently, sea disposal is totally prohibited, and thus there is a need to come up with measures to process sewage sludge on land or to convert sewage sludge into energy.

Representative methods for converting sewage sludge into energy include methods for converting sewage sludge into bio gas or into solid fuel, and besides these methods, there are also various types of technologies that are being developed, such as incineration, consolidation, carbonization and decomposition, etc. However, these methods are not in wide use due to concerns over secondary environmental pollution, low efficiency of energy conversion, soil pollution and expensive processing costs, etc.

Meanwhile, domestic and overseas power generating companies are developing technologies to utilize fat and oil, and pitch which is a byproduct of biodiesel processes, as bio-heavy oil to be mixed with bunker-C oil that is used as a fuel for power generation use in order to cope with mandatory systems to supply new renewable energies of various countries. However, most of the fat and oil used as raw material of biodiesel in South Korea is imported from abroad, and the amount is not so much either. Therefore, it is necessary to diversify the raw materials of bio-heavy oil for power generation use.

Further, of bio-fuels for transportation use, bio-ethanol made using sugar-based raw materials and bio-diesel made using vegetable oil are in commercial production, but these first generation bio-fuels have original limitations of competition with food resources, and since they contain oxygen in their molecule structure formulas, there is a disadvantage of low energy content compared to gasoline, air fuel and diesel that start from existing fossil fuels. Therefore, the interest is on breaking away from the existing first generation bio-fuels and instead producing bio-fuels (“drop-in” bio-fuels) that have no competition with food resources, and that contain low oxygen content or no oxygen at all in their molecule structure formulas.

Therefore, it is necessary to develop a technology capable of expanding and applying the substantial amount of sewage sludge inevitably being generated at home and abroad to bio-heavy oil, that is liquid phase fuel for power generation use, and possibly to liquid phase fuel for transportation use in the future through adequate conversion processes.

PRIOR ART DOCUMENTS Patents

(Patent Document 1) Korean Patent Registration No. 10-0839363

(Patent Document 2) Korean Patent Laid-open Publication No. 10-2015-0005123

SUMMARY

Therefore, a purpose of the present disclosure is to provide a method for producing bio-heavy oil having a low oxygen content and a high energy content at a high yield from sewage sludge using alcohol in a supercritical state as solvent and reaction medium, and the bio-heavy oil produced by the method.

According to an embodiment of the present disclosure, there is provided a method for producing bio-heavy oil from sewage sludge, the method including a step of producing the bio-heavy oil by reacting the sewage sludge with an alcohol solvent at a supercritical state.

The method may further include a step of drying the sewage sludge, before the step of producing the bio-heavy oil, and a step of separating and collecting a reaction product generated, after the step of producing the bio-heavy oil.

The sewage sludge may include at least one of raw sludge, excess sludge, enriched sludge, digested sludge and dehydrated sludge, and a moisture content of the sewage sludge may be 5 to 90 weight %.

The alcohol solvent may include at least one of methanol, ethanol, propanol, isopropylalcohol, butanol, isobutanol, 2-butanol, tert-butanol, n-pentanol, isopentyl alcohol, 2-methyl-1-butanol, neopentyl alcohol, diethyl carbinol, methyl propyl carbinol, methyl isopropyl carbinol, dimethyl ethyl carbinol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol and 4-heptanol.

The sewage sludge may be 1 to 80 weight % of the total 100 weight % of the sewage sludge and the alcohol solvent.

Further, the sewage sludge and the alcohol solvent may be reacted at a temperature of 250 to 600° C., under a pressure of 30 to 700 bar, for 10 seconds to 5 hours to produce the bio-heavy oil.

The alcohol solvent may be a mixed solvent where alcohol is mixed with water at a weight ratio of 7:3 to 3:7.

The step of producing the bio-heavy oil may include adding an additive and reacting the additive with the sewage sludge, and the additive may include at least one selected from a group consisting of LiOH, NaOH, KOH, RbOH, Li₂CO₃, Na₂CO₃, K₂CO₃, Mg(OH)₂, Ca(OH)₂, Sr(OH)₂, MgCO₃, CaCO₃, SrCO₃, hydrochloric acid (HCl), nitric acid (HNO₃), phosphoric acid (H₃PO₄), sulfuric acid (H₂SO₄), boric acid (H₃BO₃), hydrofluoric acid (HF), carbonic acid (H₂CO₃), formic acid (HCOOH), acetic acid (CH₃COOH), propionic acid (CH₃CH₂COOH), butylic acid (CH₃CH₂CH₂COOH), lactic acid (C₂H₄OHCOOH), and benzoic acid (C₆H₅COOH).

According to another embodiment of the present disclosure, there is provided the bio-heavy oil produced by the aforementioned producing method.

The bio-heavy oil may have an oxygen content of 5 to 20 weight %, and an O/C(oxygen/carbon) mole ratio of 0.05 to 0.25.

A higher heating value (HHV) of the produced bio-heavy oil may be 25 to 45 MJ/kg according to Math Equation 3:

$\begin{matrix} {{{Higher}\mspace{14mu} {Heating}\mspace{14mu} {Value}\left\{ {{HHV},{{MJ}\text{/}{Kg}}} \right\}} = \frac{{34\mspace{14mu} C} + {124.3\mspace{14mu} H} + {6.3\mspace{14mu} N} + {19.3\mspace{14mu} S} - {9.8\mspace{14mu} O}}{100}} & \left\lbrack {{Math}\mspace{14mu} {Equation}\mspace{14mu} 3} \right\rbrack \end{matrix}$

(In Math Equation 3 above, C, H, N, S, and O being a weight ratio of carbon, hydrogen, nitrogen, sulfur and oxygen, respectively, of total elements existing in the bio-heavy oil)

According to another embodiment of the present disclosure, there is provided a fuel for power generation use or for transportation use, the fuel including the aforementioned bio-heavy oil.

The method for producing bio-heavy oil from sewage sludge using a supercritical alcohol according to the present disclosure has an advantage of not having to use expensive hydrogen nor a heterogeneous catalyst being provided from outside, effectively converting the solid state sewage sludge into liquid state heavy oil material, and removing a certain portion of oxygen from the sewage sludge, thereby increasing the energy content.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art.

In the drawing figures, dimensions may be exaggerated for clarity of illustration. It will be understood that when an element is referred to as being “between” two elements, it can be the only element between the two elements, or one or more intervening elements may also be present between two elements. Like reference numerals refer to like elements throughout.

FIG. 1 illustrates a result of analyzing a bio-heavy oil produced using a supercritical state methanol by a gas chromatography-mass spectrometer according to Example 1 of the present disclosure.

FIG. 2 illustrates a result of analyzing a bio-heavy oil produced using a supercritical state ethanol by a gas chromatography-mass spectrometer according to Example 2 of the present disclosure.

FIG. 3 illustrates a result of analyzing a bio-heavy oil produced using a mixed solvent of which a weight ratio of ethanol:water is 3:7, as supercritical fluid, by a gas chromatography-mass spectrometer according to Example 13 of the present disclosure.

FIG. 4 illustrates a result of analyzing combustion characteristics of a bio-heavy oil produced in Example 10 of the present disclosure based on a heavy oil boiler, specifically, computational interpretation results of computational fluid dynamics (CFD) of temperature distribution inside the boiler.

FIG. 5 illustrates average gas temperatures as a function of the height of the heavy oil boiler as a result of analyzing the combustion characteristics of the bio-heavy oil produced in Example 10 of the present disclosure.

FIG. 6 illustrates results of CFD computational interpretation conducted on the heat transfer characteristics inside the heavy oil boiler by analyzing the combustion characteristics of the bio-heavy oil produced in Example 10 of the present disclosure.

FIG. 7 illustrates heat transfer rates at a boiler wall surface and each of the heat transfer pipe groups as a result of analyzing the combustion characteristics of the bio-heavy oil produced in Example 10 of the present disclosure.

DETAILED DESCRIPTION

The advantages and characteristics of the present disclosure, and the methods for achieving the same will become clearer with reference to the embodiments that will be explained in detail hereinafter. However, the present disclosure is not limited by the embodiments set forth hereinafter, but may be realized in various forms, that is, the embodiments herein are provided to complete presentation of the present disclosure, and to provide the complete range of the present disclosure to one skilled in the related art, and the present disclosure is only defined by the range of the claims.

Unless defined otherwise, all the terms (including technological and scientific terms) being used in the present specification will be used as meanings that may be commonly understood by one skilled in the art. Further, unless clearly defined otherwise, the terms defined in generally used dictionaries will not be interpreted idealistically or overly.

The present disclosure relates to a method for producing bio-heavy oil from sewage sludge and the bio-heavy oil produced by the method, and more specifically, to a method for producing a bio-heavy oil with a high yield and a high energy content from the sewage sludge by using the sewage sludge as raw material, using a supercritical state alcohol as solvent and reaction medium to convert solid phase organic material included in the sewage sludge into liquid phase organic material by a reaction of breaking the organic material into small molecules and removing oxygen existing in the molecule structure formulas of the organic material included in the sewage sludge.

The method for producing bio-heavy oil from sewage sludge according to the present disclosure may include a step of producing the bio-heavy oil by reacting the sewage sludge with an alcohol solvent at a supercritical state.

The method for producing bio-heavy oil may further include drying the sewage sludge before the step of producing the bio-heavy oil.

Further, the method for producing bio-heavy oil may further include a step of separating and collecting a reaction product generated after the step of producing the bio-heavy oil.

Hereinafter, each step of the producing method according to an embodiment of the present disclosure will be explained in detail.

First, there is no particular limitation to the sewage sludge that can be used in producing the bio-heavy oil of the present disclosure. Examples of the sewage sludge that can be used herein include organic byproducts generated in the process of treating sewage in the standard activated sludge method, and desirably, at least one of raw sludge, excess sludge, enriched sludge, digested sludge and dehydrated sludge. The content of moisture existing in the sewage sludge may be 5 to 90 weight %, and desirably, 10 to 80 weight %, and more desirably 20 to 60 weight %. If the moisture content is outside the range of 5 to 90 weight %, a bio-heavy oil with a high energy content cannot be produced at a high yield.

The step of producing the bio-heavy oil according to the present disclosure includes a step of producing the bio-heavy oil from the sewage sludge using a supercritical state alcohol. Specifically, at this step, the sewage sludge and the alcohol solvent are put into a reactor, the temperature and pressure of the reactor are raised up to or above the critical temperature and critical pressure of the alcohol to react the sewage sludge in a supercritical alcohol state. Since the process of using d supercritical state alcohol according to the present disclosure has an excellent capability of stabilizing radicals being generated during the reaction of breaking the sewage sludge into small molecules thanks to the hydrogen that is generated by itself instead of being provided from outside, it is possible to inhibit the condensation or repolymerization reaction where solid state remnants such as char/tar may be generated. Further, since it is possible to effectively remove the oxygen that exists in the sewage sludge by reactions of removing oxygen such as decarboxylation, decarbonylation, hydrodeoxygenation and the like, the 0/C (oxygen/carbon) mole ratio of the bio-heavy oil produced may be reduced, thereby increasing the energy content of the bio-heavy oil. Besides the aforementioned, it is also possible to stabilize any unstable intermediate material being generated during decomposition of the organic material existing in the sewage sludge by esterification, alkylation, alkoxylation and the like that are chemical reactivities unique to supercritical state alcohols, thereby increasing the yield of the bio-heavy oil.

The alcohol solvent being used at the step of producing the bio-heavy oil may be an alcohol solvent including one or more hydroxyl groups in a main chain having a carbon number of 1 to 10. Desirably, an alcohol of one or more hydroxyl groups combined with a main chain having a carbon number of 1 to 7 may be used, but there is no limitation thereto. The alcohol solvent may include at least one of methanol (critical temperature=239° C.; critical pressure=81 bar), ethanol (critical temperature=241° C.; critical pressure=63 bar), propanol (critical temperature=264° C.; critical pressure=52 bar), isopropylalcohol (critical temperature=307° C.; critical pressure=41 bar), butanol (critical temperature=289° C.; critical pressure=45 bar), isobutanol (critical temperature=275° C.; critical pressure=45 bar), 2-isobutanol (critical temperature=263° C.; critical pressure=42 bar), tert-isobutanol (critical temperature=233° C.; critical pressure=40 bar), n-pentanol (critical temperature=307° C.; critical pressure=39 bar), isopentyl alcohol (critical temperature=306° C.; critical pressure=39 bar), 2-methyl-1-butanol (critical temperature=302° C.; critical pressure=39 bar), neopentyl alcohol (critical temperature=276° C.; critical pressure=40 bar), diethyl carbinol (critical temperature=286° C.; critical pressure=39 bar), methyl propyl carbinol (critical temperature=287° C.; critical pressure=37 bar), methyl isopropyl carbinol (critical temperature=283° C.; critical pressure=39 bar), dimethyl ethyl carbinol (critical temperature=271° C.; critical pressure=37 bar), 1-hexanol (critical temperature=337° C.; critical pressure=34 bar), 2-hexanol (critical temperature=310° C.; critical pressure=33 bar), 3-hexanol (critical temperature=309° C.; critical pressure=34 bar), 2-methyl-1-pentanol (critical temperature=331° C.; critical pressure=35 bar), 3-methyl-1-pentanol (critical temperature=387° C.; critical pressure=30 bar), 4-methyl-1-pentanol (critical temperature=330° C.; critical pressure=30 bar), 2-methyl-2-pentanol (critical temperature=286° C.; critical pressure=36 bar), 3-methyl-2-pentanol (critical temperature=333° C.; critical pressure=36 bar), 4-methyl-2-pentanol (critical temperature=301° C.; critical pressure=35 bar), 2-methyl-3-pentanol (critical temperature=303° C.; critical pressure=35 bar), 3-methyl-3-pentanol (critical temperature=302° C.; critical pressure=35 bar), 2,2-dimethyl-1-butanol (critical temperature=301° C.; critical pressure=35 bar), 2,3-dimethyl-1-dimethyl (critical temperature=331° C.; critical pressure=35 bar), 2,3-dimethyl-2-butanol critical temperature=331° C.; critical pressure=35 bar), 3,3-dimethyl-1-butanol (critical temperature=331° C.; critical pressure=35 bar), 2-ethyl-1-butanol (critical temperature=307° C.; critical pressure=34 bar), 1-heptanol (critical temperature=360° C.; critical pressure=31 bar), 2-heptanol (critical temperature=335° C.; critical pressure=30 bar), 3-heptanol (critical temperature=332° C.; critical pressure=30 bar), and 4-heptanol (critical temperature=329° C.; critical pressure=30 bar).

Examples of the alcohol solvent may include a mixed solvent where an alcohol is mixed with water at a weight ratio of 7:3 to 3:7.

There is no particular limitation to the configuration of the reactor used at the step of producing the bio-heavy oil, but a batch type or a continuous type reactor may be used.

Further, at the step of producing the bio-heavy oil, the concentration of the sewage sludge put into the reactor may be 1 to 80 weight %, and desirably 1 to 60 weight %, of the total 100 weight % of the sewage sludge and the alcohol solvent. If the concentration of the sewage sludge is less than 1 weight %, the sewage sludge is too rare, which decreases the economic feasibility since the amount of bio-heavy oil that can be produced per unit time is too small, and if the concentration of the sewage sludge exceeds 80 weight %, the concentration is too thick, in which case there is a possibility that the breaking of the sewage sludge into small molecules and the reaction of removing oxygen may not occur effectively, and the uniformity may deteriorate, thereby decreasing the quality of the bio-heavy oil.

At the step of producing the bio-heavy oil, the temperature of reaction for the sewage sludge and the alcohol may be 250 to 600° C., and desirably, 300 to 500° C. If the reaction temperature is less than 250° C., it is difficult for the breaking of the sewage sludge into small molecules by the supercritical alcohol and the reaction of generating hydrogen and the reaction of removing oxygen to take place effectively, in which case the yield of the bio-heavy oil may decrease and the oxygen content may increase, and if the reaction temperature exceeds 600° C., the cracking reaction may occur actively, in which case the sewage sludge, that is, the raw material, may be gasified, thereby decreasing the yield of the bio-heavy oil and reducing the economic feasibility of the bio-heavy oil conversion process of the sewage sludge.

Further, at the step of producing the bio-heavy oil, the pressure of reaction between the sewage sludge and the alcohol may be 30 to 700 bar, and desirably, 100 to 500 bar. If the reaction pressure is less than 30 bar, the reaction capabilities of breaking the sewage sludge into small molecules by the supercritical alcohol, of generating hydrogen and of removing oxygen may deteriorate, thereby reducing the yield of the bio-heavy oil and increasing the oxygen content, and if the reaction pressure exceeds 700 bar, there is a problem that the processing costs for maintaining the high pressure will increase.

Further, at the step of producing the bio-heavy oil, although there is no particular limitation to the reaction time of the sewage sludge and the supercritical state alcohol, it may be 10 seconds to 5 hours, and desirably, 1 minute to 2 hours. If the reaction time is less than 10 seconds, the time is too short for the bio-heavy oil to be produced by the reaction of breaking the sewage sludge into small molecules by the supercritical alcohol, the reaction of generating hydrogen and the reaction of removing oxygen, in which case there is a possibility that the yield of the bio-heavy oil will decrease and the oxygen content will increase, and if the reaction time exceeds 5 hours, there is a problem that the processing costs will increase since a high temperature and high pressure must be maintained for a long period of time.

The step of producing the bio-heavy oil of the present disclosure may mix additional additives. Examples of the additives include materials that promote the generation of hydrogen from the supercritical alcohol or materials that promote the reaction of removing oxygen existing in the bio-heavy oil. The additive may be at least one selected from a group consisting of a material in which an alkali metal such as LiOH, NaOH, KOH, RbOH and the like is combined with a hydroxyl group; a material in which an alkali metal such as Li₂CO3, Na₂CO₃, K₂CO₃ and the like is combined with a carbonate group; a material in which an alkali earth metal such as Mg(OH)₂, Ca(OH)₂, Sr(OH)₂ and the like is combined with a hydroxyl group; a material in which an alkali earth metal such as MgCO₃, CaCO₃, SrCO₃ and the like is combined with a carbonate group; an inorganic acid such as hydrochloric acid(HCl), nitric acid(HNO₃), phosphoric acid(H₃PO₄), sulfuric acid(H₂SO₄), boric acid(H₃BO₃), hydrofluoric acid(HF), carbonic acid(H₂CO₃) and the like; and an organic acid such as formic acid(HCOOH), acetic acid(CH₃COOH), propionic acid(CH₃CH₂COOH), butylic acid(CH₃CH₂CH₂COOH), lactic acid(C₂H₄OHCOOH), and benzoic acid(C₆H₅COOH).

Further, there is no particular limitation to the usable concentration of the additive, but it may be 0.1 to 20 weight %, and desirably, 0.5 to 10 weight % of the total reaction material. If the content of the additive is less than 0.1 weight %, it may be difficult to expect effects from adding the additive when producing the bio-heavy oil from the sewage sludge, and if the content of the additive exceeds 20 weight %, the additive may exceed its soluble range in the supercritical alcohol, thereby causing concerns of overusing the additive and increasing costs for separating the additive after the process.

The present disclosure may further include a step of drying the sewage sludge before the step of producing the bio-heavy oil.

The step of drying the sewage sludge is a step of removing a certain portion of moisture existing in the sewage sludge after it is collected from a sewage treatment plant. There is no particular limitation to the drying method, and thus, natural drying and the like may be used. The content of moisture existing in the sewage sludge after the drying may be 5 to 90 weight %. Desirably, it may be 10 to 80 weight %, and more desirably, 20 to 60 weight %. If the moisture content is less than 5 weight %, it means too much energy was consumed to dry the sewage sludge, thereby increasing the overall processing costs, and if the moisture content exceeds 90 weight %, there is a problem of not being able to produce the bio-heavy oil having a high energy content at a high yield.

Further, the present disclosure may further include a step of separating and collecting the generated reaction product after the step of producing the bio-heavy oil.

The step of separating and collecting the reaction product is a step of reducing the temperature and pressure, and separating and collecting the reaction product after the step of producing the bio-heavy oil. The reaction product may be discharged through a decompression device placed in an outlet of the reactor. The reaction product may include a gas state carbon dioxide, carbon monoxide, methane, ethane, ethylene, propylene, propane, butane and the like; a liquid state material such as the produced bio-heavy oil, alcohol which is the solvent, an organic compound converted from the alcohol by participating in the reaction, and water which is a reaction byproduct; and solid state remnants such as char, tar and inorganic material. Here, the gas state product may be separated by gas-liquid separation and reducing the temperature and pressure, and the solid state remnants may be separated by solid-liquid separation using a filter, cyclone and the like. Examples of the method for separating the liquid phase bio-heavy oil from other liquid phase products or liquid phase byproducts include general distillation processes such as fractional distillation, vacuum distillation and distillation tower method, etc.

The present disclosure may provide the bio-heavy oil produced by the aforementioned method.

The yield of the bio-heavy oil produced as aforementioned may be 40 to 90 weight %, and desirably, 50 to 85 weight % according to Math Equation 1 below.

$\begin{matrix} {{{Yield}\mspace{14mu} {of}\mspace{14mu} {bio}\text{-}{heavy}\mspace{14mu} {oil}\mspace{14mu} \left( {{wt}\mspace{14mu} \%} \right)} = {\frac{{Weight}\mspace{14mu} {of}\mspace{14mu} {bio}\text{-}{heavy}\mspace{14mu} {oil}}{\begin{matrix} {{Weight}\mspace{14mu} {of}\mspace{14mu} {sewage}\mspace{14mu} {sludge}\mspace{14mu} {from}\mspace{14mu} {which}} \\ {{moisture}\mspace{14mu} {and}\mspace{14mu} {ashes}\mspace{14mu} {have}\mspace{14mu} {been}\mspace{14mu} {removed}} \end{matrix}} \times 100}} & \left\lbrack {{Math}\mspace{14mu} {Equation}\mspace{14mu} 1} \right\rbrack \end{matrix}$

The yield of the bio-heavy oil refers to the ratio of weight of the reactant and the reaction product (liquid phase) when the solid state sewage sludge is converted into liquid phase.

Further, the yield of the solid phase remnants generated according to the method for producing bio-heavy oil may be 10 to 45 weight %, and desirably, 20 to 40 weight % according to Math Equation 2 below.

$\begin{matrix} {{{Yield}\mspace{14mu} {of}\mspace{14mu} {solid}\mspace{14mu} {phase}\mspace{14mu} {remnants}\mspace{14mu} \left( {{wt}\mspace{14mu} \%} \right)} = {\frac{{Weight}\mspace{14mu} {of}\mspace{14mu} {solid}\mspace{14mu} {phase}\mspace{14mu} {remnants}}{{Weight}\mspace{14mu} {of}\mspace{14mu} {dried}\mspace{14mu} {sewage}\mspace{14mu} {sludge}} \times 100}} & \left\lbrack {{Math}\mspace{14mu} {Equation}\mspace{14mu} 2} \right\rbrack \end{matrix}$

The content of oxygen in the bio-heavy oil produced according to the method for producing bio-heavy oil may be 5 to 20 weight %, and desirably, 5 to 15 weight %.

Further, the O/C(oxygen/carbon) mole ratio of the bio-heavy oil may be 0.05 to 0.25, and desirably, 0.05 to 0.19.

The higher heating value (HHV) of the bio-heavy oil may be 25 to 45 MJ/kg, and desirably 30 to 45 MJ/kg, and more desirably, 35 to 40 MJ/kg according to Math Equation 3 below.

$\begin{matrix} {{{Higher}\mspace{14mu} {Heating}\mspace{14mu} {Value}\left\{ {{HHV},{{MJ}\text{/}{Kg}}} \right\}} = \frac{{34\mspace{14mu} C} + {124.3\mspace{14mu} H} + {6.3\mspace{14mu} N} + {19.3\mspace{14mu} S} - {9.8\mspace{14mu} O}}{100}} & \left\lbrack {{Math}\mspace{14mu} {Equation}\mspace{14mu} 3} \right\rbrack \end{matrix}$

(In Math Equation 3 above, C, H, N, S, and O are the weight ratio (weight %) of carbon, hydrogen, nitrogen, sulfur and oxygen, respectively, of the total elements existing in the bio-heavy oil)

The present disclosure may provide a fuel for use of power generation or transportation that includes the bio-heavy oil produced as aforementioned.

The fuel for use of power generation including the bio-heavy oil may be utilized as a fuel for single firing or a fuel for mixed firing, the fuel for single firing utilizing 100% of the bio-heavy oil whereas the fuel for mixed firing utilizing a certain potion of the bio-heavy oil.

Further, the fuel for use of transportation may be produced by fractionally distilling the bio-heavy oil at the boiling point and then mixing the fractionally distilled bio-heavy oil with a petroleum-based fuel for use of transportation, and the petroleum-based fuel for use of transportation may include at least one of gasoline, jet fuel and diesel.

Hereinafter, the present disclosure will be explained in further detail through the Examples and Comparative Examples below. However, these are only for exemplary purposes, and not to limit the scope of protection specified by the claims attached.

EXAMPLES Producing Bio-Heavy Oil Using Supercritical Alcohol Example 1

The sewage sludge used in the present Example is dehydrated sludge collected from a sewage terminal disposal plant, the sludge having a water content of 80%. Using a centrifuge and hot-air drying method, the sewage sludge was dried to a water content of 10 weight % to be used as the raw material. The sewage sludge used in the present disclosure consists of an ash content of 28 weight %, an organic material content of 72%, a carbohydrate/aliphatic compound content of 30 weight % of the total organic material, and an aromatic compound content of 42 weight %. The sewage sludge dried to a concentration of 10 weight % and methanol was put into a batch type reactor of 140 ml volume, the reactor was pressurized by a nitrogen of 10 bar, the temperature was raised at a speed of about 20° C./min, and at a reaction temperature of 400° C., the sewage sludge was reacted with the supercritical methanol for 30 minutes to produce bio-heavy oil. From the fact that when the temperature of the reactor reached 400° C., the reaction pressure was 365 bar, and that the reaction pressure rose to 397 bar after 30 minutes, one can see that a gasification reaction including a reaction of removing oxygen had taken place in the process of producing the bio-heavy oil. When the temperature of the reactor was reduced to normal pressure after the 30 minutes reaction, the atmospheric pressure was 25 bar. Gas phase product was collected using a Tedlar bag and then analyzed, and solid phase and liquid phase products were separated using a filter. Separation of the bio-heavy oil and methanol from the liquid phase products was conducted by fractional distillation, and then the characteristics of the separated bio-heavy oil were evaluated and stated in tables 1 to 3. Further, the bio-heavy oil produced as aforementioned was analyzed by a gas chromatography-mass spectrometer, and the results were listed in FIG. 1.

Example 2

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that ethanol was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3. The bio-heavy oil was also analyzed by a gas chromatography-mass spectrometer, and the results were listed in FIG. 2.

Example 3

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that isopropanol was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 4

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that butanol was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 5

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that the reaction temperature was 350° C. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 6

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that the reaction temperature was 300° C. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 7

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that the reaction time was 120 minutes. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 8

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that a mixed solvent of which the weight ratios of methanol:water is 7:3 was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 9

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that a mixed solvent of which the weight ratios of methanol:water is 5:5 was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 10

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that a mixed solvent of which the weight ratios of methanol:water is 3:7 was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 11

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that a mixed solvent of which the weight ratios of ethanol:water is 7:3 was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 12

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that a mixed solvent of which the weight ratios of ethanol:water is 5:5 was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 13

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that a mixed solvent of which the weight ratios of ethanol:water is 3:7 was used as the supercritical fluid. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 14

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that Na₂CO₃ of 5 weight % was used as the additive. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 15

Bio-heavy oil was produced in the same method as Example 1 above except for the fact that HCOOH of 5 weight % was used as an additive. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

Example 16

Bio-heavy oil was produced by the same method as Example 1 above except for the fact that KOH of 5 weight % was used as an additive. Then, the bio-heavy oil produced was analyzed, and the results were listed in tables 1 to 3.

<Analyzing Characteristics of the Bio-Heavy Oil>

The yields of the bio-heavy oil finally obtained in the aforementioned Examples were calculated from the weight of each component according to Math Equations 1 to 3 below.

$\begin{matrix} {{{Yield}\mspace{14mu} {of}\mspace{14mu} {bio}\text{-}{heavy}\mspace{14mu} {oil}\mspace{14mu} \left( {{wt}\mspace{14mu} \%} \right)} = {\frac{{Weight}\mspace{14mu} {of}\mspace{14mu} {bio}\text{-}{heavy}\mspace{14mu} {oil}}{\begin{matrix} {{Weight}\mspace{14mu} {of}\mspace{14mu} {sewage}\mspace{14mu} {sludge}\mspace{14mu} {from}\mspace{14mu} {which}} \\ {{moisture}\mspace{14mu} {and}\mspace{14mu} {ashes}\mspace{14mu} {have}\mspace{14mu} {been}\mspace{14mu} {removed}} \end{matrix}} \times 100}} & \left\lbrack {{Math}\mspace{14mu} {Equation}\mspace{14mu} 1} \right\rbrack \\ {{{Yield}\mspace{14mu} {of}\mspace{14mu} {solid}\mspace{14mu} {phase}\mspace{14mu} {remnants}\mspace{14mu} \left( {{wt}\mspace{14mu} \%} \right)} = {\frac{{Weight}\mspace{14mu} {of}\mspace{14mu} {solid}\mspace{14mu} {phase}\mspace{14mu} {remnants}}{{Weight}\mspace{14mu} {of}\mspace{14mu} {dried}\mspace{14mu} {sewage}\mspace{14mu} {sludge}} \times 100}} & \left\lbrack {{Math}\mspace{14mu} {Equation}\mspace{14mu} 2} \right\rbrack \\ {{{Higher}\mspace{14mu} {Heating}\mspace{14mu} {Value}\left\{ {{HHV},{{MJ}\text{/}{Kg}}} \right\}} = \frac{{34\mspace{14mu} C} + {124.3\mspace{14mu} H} + {6.3\mspace{14mu} N} + {19.3\mspace{14mu} S} - {9.8\mspace{14mu} O}}{100}} & \left\lbrack {{Math}\mspace{14mu} {Equation}\mspace{14mu} 3} \right\rbrack \end{matrix}$

(In Math Equation 3 above, C, H, N, S, and O are the weight ratio (weight %) of carbon, hydrogen, nitrogen, sulfur and oxygen, respectively, of the total elements existing in the bio-heavy oil)

Yields of the liquid phase material, solid phase material and gas phase material when producing bio-heavy oil using the supercritical alcohol calculated according to the Math Equations above were listed in table 1 below.

TABLE 1 Yield of Yield of Yield of Reaction Reaction Reaction bio-heavy solid gas phase Supercritical temperature pressure time oil remnants materials fluid (° C.) (bar) (min) Additive (wt %) (wt %) (wt %) Example 1 Supercritical 400 365-397 30 — 50.8 32.7 4.4 methanol Example 2 Supercritical 400 285-322 30 — 88.9 32.4 3.9 ethanol Example 3 Supercritical 400 239-320 30 — 53.2 34.8 3.2 isopropanol Example 4 Supercritical 400 164-197 30 — 83.6 31.3 4.2 butanol Example 5 Supercritical 350 265-277 30 — 55.4 36.0 0.3 methanol Example 6 Supercritical 300 165-186 30 — 62.3 40.2 0.2 methanol Example 7 Supercritical 400 337-406 120 — 52.9 34.0 4.4 methanol Example 8 Supercritical 400 372-402 30 — 51.4 31.3 3.7 methanol:water = 7:3 Example 9 Supercritical 400 368-393 30 — 53.9 29.9 1.2 methanol:water = 5:5 Example 10 Supercritical 400 349-363 30 — 57.5 30.1 3.0 methanol:water = 3:7 Example 11 Supercritical 400 336-362 30 — 60.8 31.4 1.0 ethanol:water = 7:3 Example 12 Supercritical 400 348-371 30 — 72.3 31.1 14.3 ethanol:water = 5:5 Example 13 Supercritical 400 336-359 30 — 51.3 29.1 1.2 ethanol:water = 3:7 Example 14 Supercritical 400 360-395 30 Na₂CO₃ 82.4 29.5 2.2 methanol Example 15 Supercritical 400 380-420 30 HCOOH 75.9 29.4 5.5 methanol Example 16 Supercritical 400 355-401 30 KOH 79.2 29.8 2.7 methanol

As shown in table 1 above, in the case of producing bio-heavy oil from sewage sludge using the supercritical methanol, ethanol, isopropanol and butanol in Examples 1 to 4, one can see that the liquid phase yield of the bio-heavy oil produced is 50 to 89 weight %, the yield of the solid remnants is 31 to 35 weight %, the yield of the gas phase materials is less than about 5 weight %, that is, the yield of the liquid phase materials is very high. Considering that the inorganic components included in the sewage sludge, i.e. the raw material, that cannot be converted into gas phase nor liquid phase material is 28 weight %, 3 to 7 weight % of organic materials exist in the 31 to 35 weight % of the solid remnants, which means that most of the organic materials were converted into the gas phase or liquid phase materials, and since the yield of the gas phase materials is 5 weight %, which is quite low, one can see that most of the organic materials existing in the sewage sludge were converted into liquid phase materials. This is considered to be because condensation or repolymerization reaction that generates solid state remnants could be inhibited since the supercritical alcohol could provide hydrogen effectively, and because reactions such as esterification, alkylation, alkoxylation and the like could take place effectively even without using a catalyst, thereby stabilizing the unstable intermediate matter generated during decomposition of the organic materials existing in the bio-heavy oil and increasing the liquid phase yield.

Meanwhile, in the case of lowering the reaction temperature of the supercritical methanol in Example 5 and Example 6 to 350° C. and 300° C., respectively, to produce bio-heavy oil, from the fact that the yield of the solid remnants increased to 36 weight % and to 40 weight %, respectively, one can see that the conversion ratio of the organic materials existing in the sewage sludge was somewhat reduced, but the liquid phase yield was maintained at a high level of 55 to 62 weight %.

Meanwhile, from the fact that the yield of the solid remnants was maintained at a low level of 34 weight % even when the reaction time was increased to 120 minutes in Example 7, one can see that most of the organic materials existing in the sewage sludge were converted into liquid phase and gas phase materials. Meanwhile, from the fact that the liquid phase yield was maintained at a very high level of 53 weight % and that the gas phase yield was 4 weight %, which is very similar to the gas phase yield of Example 1, one can see that gasification reaction that may occur due to a long term reaction was inhibited.

Meanwhile, in the case of using mixtures having various weight ratios of methanol:water in Example 8 to Example 10 as the supercritical solvent, from the fact that the yield of the solid remnants is 30 to 31 weight %, which is very similar to 28 weight % the content of inorganic materials that the sewage sludge has, one can seen that most of the organic materials in the sewage sludge were converted into liquid phase and gas phase materials. Further, one can see that the liquid phase yield was maintained at a very high level of 51 to 58 weight %, and the gas phase yield was 3 to 4 weight %, meaning that most of the organic materials were converted to liquid phase materials.

Further, also in the case of using mixtures having various weight ratios of methanol:water in Example 11 to Example 13, one can see that most of the organic materials existing in the sewage sludge were converted into liquid phase materials very similarly as in Example 8 to Example 10.

Meanwhile, in the case of using Na₂CO₃, HCOOH, and KOH as the additive in Example 14 to Example 16, from the fact that the yield of the solid remnants was 30 weight %, which is very similar to 28 weight %, the content of inorganic materials in the sewage sludge, one can see that most of the organic materials existing in the sewage sludge were converted into liquid phase and gas phase materials. Further, from the fact that the yield of the liquid phase was 75 to 83 weight %, which is higher when compared to Example 1, and that the yield of the gas phase is 2 to 6 weight %, one can see that the most of the organic materials were converted into liquid phase materials.

Next, the characteristics of the sewage sludge before the reactions and the characteristics of the bio-heavy oil produced after the reactions were analyzed and listed in table 2, and the components of the gas reaction products were analyzed and listed in table 3.

Analyses on the elements of the reactants were conducted using an elemental analyzer (EA, Vario EL cube, Elementar Analysensystem GmbH) equipped with a thermal conductivity detector (TCD).

Meanwhile, qualitative and quantitative analyses on the gas reaction products were conducted using the gas chromatography (GC, Clarus 600 GC-Model Arnel 1115PPC Refinery Gas Analyzer (RGA), PerkineElmer)) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID).

TABLE 2 C O H N S HHV (wt (wt (wt (wt (wt O/C (MJ/ %) %) %) %) %) ratio kg) Sewage 38.9 23.2 3.6 6.4 1.1 0.45 16.3 sludge Example 1 71.8 13.2 6.6 6.2 0.8 0.14 32.0 Example 2 71.5 8.2 7.2 5.0 1.2 0.09 33.1 Example 3 70.3 10.5 8.3 7.0 2.2 0.11 34.2 Example 4 71.5 10.8 9.2 6.5 2.1 0.11 35.6 Example 5 66.5 14.8 8.1 7.2 0.9 0.17 32.0 Example 6 58.8 15.1 7.8 7.7 0.7 0.19 29.0 Example 7 73.3 9.6 8.2 5.2 0.5 0.10 34.7 Example 8 72.1 11.4 9.0 5.4 0.7 0.12 35.2 Example 9 74.3 9.0 9.0 4.9 0.9 0.09 36.1 Example 10 76.0 9.1 9.1 5.1 0.9 0.09 36.8 Example 11 71.0 10.2 9.2 5.7 1.1 0.11 35.2 Example 12 71.8 10.9 8.9 5.5 1.3 0.11 35.1 Example 13 75.5 8.0 9.4 5.3 1.8 0.08 37.3 Example 14 68.0 9.2 8.8 6.8 0.9 0.10 33.8 Example 15 71.2 9.5 8.2 5.4 1.0 0.10 34.1 Example 16 70.8 9.3 9.1 5.1 0.9 0.10 35.1

TABLE 3 C₂H₄+ C₃H₆+ Yield of CO₂ CO H₂ CH₄ C₂H₆ C₃H₈ C4+ gas phase (mol %) (mol %) (mol %) (mol %) (mol %) (mol %) (mol %) (wt %) Example 1 31.6 10.9 23.6 7.7 21.2 3.7 1.1 4.4 Example 2 23.3 6.8 3.6 48.9 4.9 2.2 0.7 3.9 Example 3 33.0 3.8 0.2 49.0 6.8 4.0 2.2 3.2 Example 4 15.0 19.2 19.0 6.5 19.6 19.7 0.8 10.4 Example 5 14.8 15.2 20.2 4.2 15.8 8.9 0.5 0.3 Example 6 0.8 2.2 95.3 0.4 21.2 0.1 0.0 0.2 Example 7 30.0 28.3 1.8 7.1 29.1 3.2 0.4 4.4 Example 8 37.3 7.0 10.0 30.9 9.7 3.2 1.7 3.7 Example 9 51.0 12.1 7.4 10.3 16.7 2.4 0.0 1.2 Example 10 20.0 13.5 33.0 6.1 23.3 3.1 0.9 3.0 Example 11 21.4 24.5 0.5 7.2 42.1 3.5 1.3 1.0 Example 12 13.7 54.6 4.3 5.9 19.8 1.1 0.5 14.3 Example 13 69.0 8.0 0.5 5.8 14.3 1.5 0.4 1.2 Example 14 35.2 15.2 12.2 7.8 15.3 3.4 4.2 2.2 Example 15 33.4 17.8 13.2 7.2 17.4 4.5 4.6 5.5 Example 16 25.8 25.2 11.0 8.9 19.9 3.1 2.8 2.7

As shown in table 2, the sewage sludge had a low carbon content of 38.9 weight %, and a high oxygen content of 23.2 weight %, and a high 0/C(oxygen/carbon) mole ratio of 0.45, and thus the higher heating value (HHV) was 16.3 MJ/kg, which is very low.

In the case of producing bio-heavy oil using the supercritical alcohol in Example 1 to Example 4, from the fact that the carbon content of liquid phase materials increased and the oxygen content decreased and the 0/C mole ratio decreased to 0.09 to 0.14, one can see that the deoxygenation reaction occurred effectively, and from the fact that the HHV increased significantly to 32.0 to 35.6 MJ/kg, one can see that the energy content increased.

As illustrated in table 3, an excess amount of CO(10.9 mol %) and CO₂(31.6 mol %) was detected as a result of analyzing the components of the gas product of Example 1, meaning that the oxygen included in the sewage sludge was removed by the decarbonylation reaction and decarboxylation reaction, and from the fact that an excess amount of H₂(23.6 mol %) was detected, one can see that the methanol in a supercritical state generated hydrogen, so that the recombination or condensation reaction that may occur in the sewage sludge conversion reaction was inhibited even without the hydrogen being provided from outside, thereby increasing the yield of the liquid phase material produced. Further, from the fact that a small amount of C₃H₆+C₃H₈(3.7 mol %) and C₄+(1.1 mol %) was detected, one can see that the cracking reaction of the organic materials included in the sewage sludge was inhibited.

Meanwhile, in the case where the reaction temperature was maintained at 350° C. and 300° C. in Example 5 and Example 6, respectively, the 0/C mole ratio each decreased to 0.17 and 0.19, respectively, and even though the HHV decreased to 32.0 and 29.0 MJ/kg, respectively, which are somewhat lower than the HHV of Example 1, one can see that they are quite high when compared to the HHV of the sewage sludge.

Meanwhile, even when the reaction time was increased to 120 minutes in Example 7, the 0/C mole ratio decreased significantly to 0.1, and the HHV increased significantly to 34.7 MJ/kg, and most of the generated gas was CO(28.3 mol %) and CO₂(30.0 mol %), meaning that the decarbonylation and decarboxylation reaction occurred actively, thereby effecting removing the oxygen.

Meanwhile, in the case of using the mixture of methanol:water of various weight ratios as the supercritical solvent in Example 8 to Example 10, the 0/C mole ratio decreased significantly to 0.09 to 0.12, and the HHV increased significantly to 35.2 to 36.8 MJ/kg, and from the fact that most of the generated gas is CO and CO₂, one can see that the decarbonylation and decarboxylation reaction occurred actively, thereby effectively removing the oxygen, and from the fact that the content of hydrogen is 7.4 to 33.0 mol %, one can see that generation of hydrogen occurred actively in the mixed solvent as well.

Further, in the case of using the mixture of ethanol:water having various weight ratios as the supercritical solvent in Example 11 to Example 13, from the fact that the 0/C mole ratio decreased significantly to 0.08 to 0.11, and the HHV increased significantly to 35.1 to 37.3 MJ/kg, and most of the generated gas is CO and CO₂, one can see that the decarbonylation and decarboxylation reaction occurred actively, thereby effectively removing the oxygen, and from the fact that a small amount of C3+ and C4+ was generated, one can see that the cracking reaction was inhibited effectively.

Meanwhile, in the case of using Na₂CO3, HCOOH and KOH as the additive in Example 14 to Example 16, from the fact that the O/C mole ratio further decreased to 0.1 when compared to Example 1, and the HHV further increased to 33.8 to 35.1 MJ/kg, one can see that the deoxygenation reaction occurred more actively. Further, from the fact that most of the generated gas is CO and CO₂ even when using the additive, one can see that the decarbonylation and decarboxylation reaction occurred actively, thereby effectively removing the oxygen, and from the fact that a small amount of C3+ and C4+ was generated, one can see that the cracking reaction was inhibited effectively.

Experiment Example

In order to find out the applicability of the bio-heavy oil produced in the Examples to thermal power plants, Computational Fluid Dynamics (CFD) was conducted on a Ulsan thermal power heavy oil boiler. The size of the Ulsan thermal power heavy oil boiler was 10 m×12.6 m×56 m, the heat input was 1025 MW_(th), and the counterflow method of 405 MWe turbine output was used. Combustion characteristics of the bio-heavy oil produced in Example 10 were analyzed based on the Ulsan fire power heavy boiler.

The Computational Fluid Dynamics (CFD) on the Ulsan heavy oil boiler was conducted by interpreting the emulsion single firing conditions of heavy oil that take place in petrochemical refineries and on mixed firing conditions of 80 weight % of petrochemical heavy oil emulsion and 20 weight % of sewage sludge-derived bio-heavy oil, and then comparing and analyzing the interpretation results.

The Ulsan thermal power boiler is a boiler of 405 MW_(e) turbine output, wherein the heat input capacity is about 1025 MW_(th). Ulsan thermal power heavy oil boiler uses a swirl burner and the flow rate was divided evenly. Further, interpretation was conducted after setting the swirl direction to the gear train method. The axial:tangential ratio of the swirl of the burner was assumed as being 1:0.8. The interpretation conditions of the Ulsan thermal power heavy oil boiler are as stated in Table 4 below.

TABLE 4 Operating conditions Heavy oil Heavy oil 80% + Bio-heavy oil 20% Heat input capacity (MW_(th)) 1025.1 1025.0 Turbine output (MW_(e)) 405.1 405.0 Fuel Throughput 24.697 19.75 (Heavy oil)/ 5.93 (Bio-heavy oil) Temperature (° C.) 107 107 Bio-heavy oil Water content (%) 0.5 5.39 Volatile component 94.342 94.38 (%) Fixed carbon (%) 5 0 Ash (%) 0.158 0.23 C (%) 86.5 73.26 H (%) 10.8 8.198 O (%) 0.202 9.558 N (%) 0.458 5.19 S (%) 2.04 0.453 HHV (MJ/kg) 41.51 34.59 Emulsion water Flow rate (kg/s) 2.57 2.06 Atomized Temperature (° C.) 346 346 steam Flow rate (kg/s) 1.611 1.611 Air Excess air (%) 1.19 4.6 Flow rate (kg/s) 344.25 361 Temperature (° C.) 312 312

CFD computational interpretation results of temperature distribution sorted per condition in the boiler are shown in Table 4. The temperature atmosphere inside the boiler in the case of mixed-firing 20% of bio-heavy oil was higher than that under the heavy oil single-firing condition. This is considered to be because the ignition of bio-heavy oil occurred faster than the emulsion type heavy oil that contains moisture, increasing the gas temperature inside the boiler. Since the gear train method is used as in heavy oil single firing and the inside of the boiler has a symmetrical structure, not only the temperature distribution but also most of the characteristics such as the flux, chemical species, heat flux distribution and the like showed front-back and left-right symmetric forms, meaning that mixed firing of the bio-heavy oil is possible.

Meanwhile, FIG. 5 illustrates average gas temperatures as a function of boiler height. One can see that the average gas temperatures under the condition of mixed firing 20% of bio-heavy oil were high overall.

Further, CFD Computational Interpretation was conducted to analyze the heat transfer characteristics inside the boiler, and its results are as shown in FIG. 6. The results under the condition of mixed firing 20% of bio-heavy oil showed a symmetric trend just as the condition of single firing heavy oil, and the heat flux was the highest in front of the burner of the third column. The maximum heat flux under the condition of single firing heavy oil was 480 kW/m², and the maximum heat flux under the condition of mixed firing bio-heavy oil was 364 kW/m², meaning that the maximum heat flux is lower under the mixed firing condition. However, the overall trend is similar and the mixed firing condition showed more consistent distribution of wall surface heat flux, confirming that it is possible to mixed-fire the bio-heavy oil produced from sewage sludge. Such difference in distribution of wall surface heat flux is considered to be because of differences in radiation characteristics caused by the amount of soot. The more heavy oil there is in the fuel being input, the more soot is generated, and thus soot was generated the most under the condition of single-firing heavy oil up to 3 weight %, whereas in the case of mixed-firing, concentrations of soot decreased.

FIG. 7 illustrates heat transfer rates at a boiler wall surface and each heat transfer pipe group. According to FIG. 7, in the case of single-firing heavy oil, the heat transfer rate was the highest, 473 MW_(th), and in the case of mixed-firing 20% of bio-heavy oil, the heat transfer rate of the wall surface slightly decreased to 425 MW_(th). In the case of mixed firing 20% of bio-heavy oil, as the heat transfer rate of the wall surface decreased, the heat transfer rate in the rear column heat transfer rate group increased by as much as 3˜9 MW_(th) per heat transfer rate group.

Therefore, the results of the computational interpretation of the single-firing heavy oil and mixed-firing bio heavy oil confirmed that it is possible to conduct mixed firing using the bio-heavy oil produced from sewage sludge.

The advantages of the present invention are verified from the above examples, but the present invention is not limited by them. Various substitutions, alterations, and modifications are possible in the range without departing from the technical idea of the present invention. Thus the above description does not limit the scope of the present invention defined by limits of the following claims. 

What is claimed is:
 1. A method for producing bio-heavy oil from sewage sludge, the method comprising a step of producing the bio-heavy oil by reacting the sewage sludge with an alcohol solvent at a supercritical state.
 2. The method according to claim 1, further comprising a step of drying the sewage sludge, before the step of producing the bio-heavy oil.
 3. The method according to claim 1, further comprising a step of separating and collecting a reaction product generated, after the step of producing the bio-heavy oil.
 4. The method according to claim 1, wherein the sewage sludge comprises at least one of raw sludge, excess sludge, enriched sludge, digested sludge and dehydrated sludge.
 5. The method according to claim 4, wherein a moisture content of the sewage sludge is 5 to 90 weight %.
 6. The method according to claim 1, wherein the alcohol solvent comprises at least one of methanol, ethanol, propanol, isopropylalcohol, butanol, isobutanol, 2-butanol, tert-butanol, n-pentanol, isopentyl alcohol, 2-methyl-1-butanol, neopentyl alcohol, diethyl carbinol, methyl propyl carbinol, methyl isopropyl carbinol, dimethyl ethyl carbinol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 2,3-dimethyl-2-butanol, 3,3-d imethyl-1-buta nol, 2-ehtyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol and 4-heptanol.
 7. The method according to claim 1, wherein the sewage sludge is 1 to 80 weight % of a total 100 weight % of the sewage sludge and the alcohol solvent.
 8. The method according to claim 1, wherein the sewage sludge and the alcohol solvent are reacted at a temperature of 250 to 600° C.
 9. The method according to claim 1, wherein the sewage sludge and the alcohol solvent are reacted under a pressure of 30 to 700 bar.
 10. The method according to claim 1, wherein the sewage sludge is reacted at the supercritical state of the alcohol solvent for 10 seconds to 5 hours.
 11. The method according to claim 1, wherein the alcohol solvent comprises a mixed solvent where the alcohol is mixed with water at a weight ratio of 7:3 to 3:7.
 12. The method according to claim 1, wherein the step of producing the bio-heavy oil comprises adding an additive and reacting the additive with the sewage sludge.
 13. The method according to claim 12, wherein the additive comprises at least one selected from a group consisting of LiOH, NaOH, KOH, RbOH, Li₂CO₃, Na₂CO₃, K₂CO₃, Mg(OH)₂, Ca(OH)₂, Sr(OH)₂, MgCO₃, CaCO₃, SrCO₃, hydrochloric acid (HCl), nitric acid (HNO₃), phosphoric acid (H₃PO₄), sulfuric acid (H₂SO₄), boric acid (H₃BO₃), hydrofluoric acid (HF), carbonic acid (H₂CO₃), formic acid (HCOOH), acetic acid (CH₃COOH), propionic acid (CH₃CH₂COOH), butylic acid (CH₃CH₂CH₂COOH), lactic acid (C₂H₄OHCOOH), and benzoic acid (C₆H₅COOH).
 14. A bio-heavy oil produced by the producing method of claim
 1. 15. The bio-heavy oil according to claim 14, wherein the bio-heavy oil has an oxygen content of 5 to 20 weight %, and an O/C(oxygen/carbon) mole ratio of 0.05 to 0.25.
 16. The bio-heavy oil according to claim 14, wherein a higher heating value (HHV) of the bio-heavy oil may be 25 to 45 MJ/kg according to Math Equation 3: $\begin{matrix} {{{Higher}\mspace{14mu} {Heating}\mspace{14mu} {Value}\left\{ {{HHV},{{MJ}\text{/}{Kg}}} \right\}} = {\frac{{34\mspace{14mu} C} + {124.3\mspace{14mu} H} + {6.3\mspace{14mu} N} + {19.3\mspace{14mu} S} - {9.8\mspace{14mu} O}}{100}.}} & \left\lbrack {{Math}\mspace{14mu} {Equation}\mspace{14mu} 3} \right\rbrack \end{matrix}$ in Math Equation 3 above, C, H, N, S, and O being a weight ratio of carbon, hydrogen, nitrogen, sulfur and oxygen, respectively, of total elements existing in the bio-heavy oil.
 17. A fuel for use of power generation or for transportation, the fuel comprising the bio-heavy oil according to claim
 14. 